Circuit breakers are used extensively to prevent excessive current from flowing through electrical circuits and thereby damaging circuit components. Well known circuit breakers include fuses and electro-mechanical circuit breakers which physically open the circuit by disconnecting the power supply from the circuit components to be protected in response to excessive currents.
In the operation of fuses and electro-mechanical circuit breakers, there is a relatively long time period between the occurrence of the overcurrent and actual interruption of current flow. As a result, when fuses and electro-mechanical circuit breakers are relied upon for protection, overcurrents often damage sensitive circuit components before the circuit is opened. In addition, fuses and electro-mechanical circuit breakers are either destroyed or subject to mechanical wear when opening a circuit and must be replaced frequently.
In recent years, the use of electronic circuit breakers has become increasingly prevalent due to the increased speed and absence of mechanical wear afforded by solid state circuitry. Present electronic circuit breakers are capable of sensing an overcurrent and interrupting current flow in several microseconds. However, even exposure to several microseconds of a relatively small overcurrent can damage very sensitive circuit components.
Therefore, a need exists for a high speed electronic circuit beaker which has a response time of under one microsecond.
In addition, there is an inherent time delay in electronic circuit breakers between the sensing of an overcurrent and the actual interruption of current flow. Present electronic circuit breakers do not limit the rate at which the current can increase during this time delay. Consequently, in present circuit breakers current can increase dramatically during this time delay resulting in extremely large values of overcurrent capable of damaging even circuit components designed to handle high power.
Therefore, a need exists for an electronic circuit breaker which limits the rate at which the current can increase during the time delay between the sensing of an overcurrent and interruption of current flow.